Originally Posted by Fraser

I mean, I did figure out I was doing it wrong I just didn't realise you could get different C availability by searching a connecting itinerary versus segment by segment, especially when EF shows the availability on each flight if you search that connecting itinerary.

I should therefore assume that in this case it's the same as C = 0 on any other flight. I see some other options out there where I can get FC reasonably so I'll just do that and lose the vouchers...